Wireless bandwidth is one of the most valuable resources in mobile communication networks. In many such networks, both communication traffic and control messages share a limited amount of wireless bandwidth. Unfortunately, control messages often require significant amounts of wireless bandwidth to ensure proper operation of the network. For example, to effectively provide communication services to mobile terminals, mobile communication networks typically use control messages to track and manage the locations of the terminals within the networks.
A typical mobile communication network (e.g., a cellular network) is made up of interconnected base stations that form a network backbone. Each base station provides wireless signal coverage for a specific geographic area, commonly referred to as a cell. Sets of network cells are grouped into location areas, which are used for tracking and managing the locations of mobile terminals (e.g., cellular telephones) in the network.
Mobile communication networks track mobile terminals through operations known as registration and paging. Registration refers to operations for updating the tracked location areas of mobile terminals, and paging refers to operations for locating mobile terminals in the tracked location areas. Unfortunately, conventional registration and paging operations often impose a significant load on wireless bandwidth resources, especially during times of high call volume or when networks provide service to significant numbers of mobile terminals.
With respect to the function of registering when a mobile terminal crosses a boundary of a location area, the mobile terminal registers its new location (a new location area) by providing updated location information to a location management database maintained by the network. Consequently, the network is typically aware of the location area in which a mobile terminal is located at all times.
The function of paging refers to the mobile communication network locating mobile terminals. For example, when a telephone call directed to a particular mobile terminal arrives at the mobile communications network, the network looks in the location management database to determine in which location area the terminal is located. The network then searches the identified location area to determine the specific cell in which the mobile terminal is located by broadcasting a paging message to all of the cells in the location area. The wireless terminal responds to the paging message and indicates its cell location. The mobile communication network then sends the incoming telephone call to the base station of the indicated cell so that the telephone call may be connected.
Both registration and paging operations impose costs on mobile communication networks, namely by reducing the overall available wireless bandwidth. The cost of registration is typically measured according to the number of registration operations performed, and the cost of paging is typically measured according to the number cells to which paging messages are broadcast before a mobile terminal is located.
Clearly, there is a tradeoff between the costs of registration and paging, and the tradeoff depends upon the size (i.e., the number of cells) of a location area. At one extreme, if each location area contains only one cell, paging costs will be at a minimum. However, registration costs will be at a maximum as wireless terminals register their new locations at every instance of moving from one cell to another. The other extreme occurs if the entire service area covered by the mobile communication network is defined as a single location area. In this scenario, registration costs will be at a minimum, but paging costs will be at a maximum because each paging operation would poll every cell in the network. Consequently, network designers carefully design location areas to balance the costs of registration and paging operations.
Several approaches have been introduced for minimizing paging costs without increasing registration costs. The existing approaches typically divide the cells of a location area into groups that may be polled sequentially until a mobile terminal is located. These groups of cells within a location area are commonly referred to as paging areas. Paging costs are reduced whenever the mobile terminal is located before every paging area in a location group is polled.
To increase the chance that the mobile terminal will be located early in the polling sequence, location probabilities are often used to prioritize cells or groups of cells that are relatively more likely to contain the mobile terminal. Accordingly, paging messages are theoretically broadcast to the paging areas sequentially, generally starting with the paging area having the highest probability of containing the mobile terminal and moving through the paging areas in decreasing order of location probabilities. Delay bounds have been imposed in several such existing approaches in order to ensure that the mobile terminal is found within an acceptable amount of time.
While existing probability-based paging approaches (e.g., reverse paging, semi-reverse paging, selective paging, and uniform paging) have generally helped to reduce the average costs of paging operations in many mobile communication networks, the level of success of each of the existing approaches is dependent upon factors such as network architectures, location distribution patterns of mobile terminals, Quality of Service (“QoS”) requirements, and network applications. For example, a particular paging approach may perform better for uniform location probability distributions than for irregular location probability distributions. Accordingly, network designers often select a paging approach based on its predicted performance as applied to the specific characteristics of a mobile communications network.
Given the vast range of different types and applications of mobile communications networks, there exists at least a need for additional paging processes so that network designers have increased options for matching the most effective paging technique to a particular mobile communication network. It would be desirable to have a paging approach that effectively reduces paging costs for a wide variety of location distribution patterns, network architectures, and network applications. It would be further desirable for the paging approach to effectively locate mobile terminals while remaining within a predetermined delay bound of a network.